1. Field of the Invention
The present invention relates to an apparatus and method of generating a write pulse appropriate for a variety of optical recording media, and more particularly, to an apparatus and method of generating a write pulse so as to be compatible with a variety of optical recording media at a variety of speeds for recording.
2. Description of the Related Art
Optical recording media proposed presently can be divided into Compact Discs (CDs) and Digital Versatile Discs (DVDs). Optical apparatuses for CD-Rs and CD-RWs, which are types of CDs, are standardized and are widely used. Optical apparatuses for DVD-RWs, DVD-Rs, DVD+RWs, and DVD-RAMs, which are types of DVDs, are also presently offered. However, since write characteristics are different for these CD and DVD types, the types of write pulses for the optical recording media are also different. Also, since the write characteristics are different according to the speed for recording of each optical recording medium, the types of the write pulses vary depending on the speed for recording of the optical recording medium.
For example, a multi-pulse train for the write pulses of the DVD-RAM or the CD-RW starts from a “high” logic level in a channel clock, and are referred to as an “on-start” pulse type. Additionally, the multi-pulse train for the write pulses of the DVD±RW or the DVD-R starts from a “low” logic level in a channel clock, and thus can be referred to as an “off-start” multi-pulse type. Further, the write pulse of the CD-R is not the multi-pulse but is similar to a Non-Return to Zero Invert (NRZI). Therefore, the write pulse of the CD-R can be referred to as the Non-Multi-pulse type.
Therefore, in order to accommodate a variety of optical recording media types in one optical apparatus, there has been proposed an apparatus which generates a write pulse appropriate for each optical recording medium type. The write pulse generating apparatus counts the start position and the end position of each of a first pulse, a multi-pulse train, a last pulse, and a cooling pulse (also referred to as a bottom pulse) forming a write pulse appropriate for each optical recording medium type. The count is on the basis of the start point and the end point of a write mark (domain). Then, using the counted values, the apparatus generates a bias 3 control signal (also referred to as a bottom control signal), an erase control signal (also referred to as a bias 1 control signal), a peak control signal and a cooling control signal (also referred to as a bias 2 control signal) so as to control a Laser Diode (LD) driving unit to generate a desired write pulse.
Also, a write pulse generating apparatus has been proposed which changes a pulse width of the multi-pulse train in order to provide a write pulse appropriate for high density and high speed factor optical recording media.
However, in these write pulse generating apparatuses, a write current channel, which is input to an LD driving unit, is fixed. That is, the current transmission channel, which is input to the LD driving unit, is fixedly formed with a read current transmission channel, a peak current transmission channel, an erase current transmission channel, a cooling current transmission channel, and a bottom current transmission channel. Also, signals for controlling the LD driving unit fixedly include a bias control signal, an erase control signal, a peak control signal, and a cooling control signal. In addition, these conventional write pulse generating apparatuses mainly use a method which varies the width of the write pulse.
However, as higher speed factor media are being developed, the width of the write pulse of the write mark (domain) is being proportionately narrowed. Also, as users demand one optical apparatus to record and reproduce data for all kinds of optical recording media, the types of write pulses required for recording and reproducing data for each type of optical recording medium become more diversified. Therefore, a method which varies the width of the write pulse, in which the current transmission channels and the number of control signals used in selecting current transmission channels are fixed, as in the conventional write pulse generating apparatuses, cannot satisfy the demands for providing a variety of write pulse types.